Bookbinding processing apparatus, and image forming system including bookbinding processing apparatus

An image forming system comprising:

• an image forming unit configured to form an image on a sheet;
• a conveyance path configured to convey the sheet with the image formed the image forming unit from the image forming unit to an unloading port;
• a bookbinding processing unit configured to, provided on a lower side of the conveyance path, perform bookbinding processing including binding and folding for a sheet bundle;
• a bookbinding processing path configured to convey the sheet from the conveyance path to the bookbinding processing unit;
• a conveyance unit configured to, provided in the conveyance path, convey the sheet;
• a detection unit configured to detect that the sheet conveyed by the conveyance unit reaches a predetermined position;
• a buffer path provided on an upper side of the conveyance path and configured to buffer the sheet;
• a buffer conveyance unit configured to, provided in the buffer path, convey the sheet;
• a conveyance control unit configured to control the conveyance unit to feed a preceding sheet conveyed through the conveyance path to the buffer path;
• and
• a buffer conveyance control unit configured to control the buffer conveyance unit to convey the preceding sheet from the buffer path to the conveyance path based on a detection result of a subsequent sheet following the preceding sheet by the detection unit,
• wherein the conveyance control unit controls the conveyance unit to feed bundle of the preceding sheet and the subsequent sheet to the bookbinding processing path.